What happens is that you reduce calories, and then you lose some weight, and then you reduce It some more, but what ends up happening is that you reach a limit where you don’t function as well. You’re constantly hungry, tired and cranky. You get headaches. You don’t sleep well. You get cold extremities; you start losing muscle mass. Eventually, the negative consequences outweigh the good (e.g. weight loss), and then we quit and regain a good portion (or more – known as rebound weight gain).